Centrifugal switch having two resilient arms with adjustable force transmitting means functioning therebetween



July 13, 1965 N. K. LINDGREN 3,194,913

CENTRIFUGAL SWITCH HAVING TWO RESILIENT ARMS WITH ADJUSTABLE FORGETRANSMITTING MEANS FUNCTIONING THEREBETWEEN Filed June 27, 1960 2Sheets-Sheet 1 40 4 58 27 26 Twzzvron W16 Km '9 July 133, 1965 N. K.LINDGREN GENTRIFUGAL SWITCH HAVING TWO RESILIEN'I' ARMS WITH ADJUSTABLEFORCE TRANSMITTING MEANS FUNCTIONING THEREBETWEEN 2 Sheets-Sheet 2 FiledJune 27. 1960 INVENTOR.

Arman Er United States Patent 3 194,913 CENTRIFUGAL SWlTt'lH HAVENG TWt)RESILIENT ARMS WITH ADJUSTABLE FQRCE TRANSMlT- TlNG MEANS FUNQTiONINtGTHEREBETWEEN Nils Kauri Lindgren, Stockholm, Sweden, assignor toAlrtieholaget Electrolux, Stoclrhoim, Sweden, :1 corporation of SwedenFiled June 27, 1969, Ser. No. 39,082 Claims priority, applicationSweden, July 3, 1959, 6 322/59 8 Claims. (Cl. 20tl-80) This inventionrelates to electric motors and more particularly to a regulating devicefor controlling the supply of electric current thereto. I

In order to avoid objectionable current surges when a motor is connectedto a source of electrical supply, electric motors are often providedwith a starting resistor which is connected in the motor circuit whenoperation of the motor is first started. After the motor has beenstarted, such starting resistor is cut out of the motor circuit, andagain connected in the motor circuit when the motor is stopped.

it is an object of the invention to provide an improvement forregulating the current supply to electric motors. More particularly, itis an object to provide such an improvement for regulating the currentsupply to electric motors provided with a starting resistor.

In accordance with the invention, this is accomplished by providing acentrifugally actuated control device having a switch which is mountedfor rotation on the motor and includes a first fixed contact and asecond movable contact which cooperates therewith and is mounted on aresilient arm whose tension is adjustable.

The above and other objects and advantages of the invention will be morefully understood upon reference to the following description andaccompanying drawing forming a part of this specification, and of which:

FIG. 1 is a semi-diagrammatic side elevational view of an electricalmotor equipped with a regulator constructed in accordance with thisinvention;

FIG. 2 is an end elevational view, larger in scale than in FIG. 1, ofthe regulator employed in the device of FIG. 1;

FIG. 3 is a fragmentary sectional view taken at line 3-3 of FIG. 2;

FIG. 4 is a view taken at line 44 of FIG. 2; and

FIG. 5 is a schematic diagram illustrating the electrical circuits forthe motor and regulator in the device of FIG. 1.

Referring to the drawing, the universal electrical motor shown comprisesa housing in which are mounted the usual armature 11 and stator 12, thestator being provided with an electromagnetic winding 13 and thearmature with an electromagnetic winding 14, as seen in FIG. 5. Thenovel speed regulator of the invention is indicated generally at 16,being mounted on the motor shaft 15. In addition, the motor is equippedwith a manual start-stop switch 17 and a suitable input connector 18.The motor is mounted on a base 19 and connected to the driven device bya coupling 20 formed of suitable insulating material.

As seen in FIG. 2, the regulator 16 includes a combined capacitor andmount 21, a centrifugal switch 22 and a resistor assembly 23. Thecombined capacitor and mount comprises a pair of flat circular metallicplates 24 and 25 which are disposed face to face and transverselypositioned with respect to shaft 15. A thin sheet 26 of mica or othersuitable dielectric material is disposed between and in direct contactwith the plates 24 and 25.

The plates 24 and 25 and the dielectric sheet 26 therebetween are firmlyclamped together by hollow rivets 27 extending through aligned openingsin these members, one head portion of each rivet directly engaging plate24 and the other head portion being electrically insulated from plate 25by a flanged insulating washer 28, as seen in FIG. 3. Accordingly,device 21 is a laminated capacitor having electrically separated plates24 and 25.

The combined capacitor and mount 21 is secured to shaft 15 by a member29 having a bore 30 to receive the shaft, the hub having a set screw 31for securing it to the shaft 15, as seen in FIG. 3. The member 29includes a shoulder portion 32, an intermediate portion 33 and athreaded tip 34. Portion 33 is enveloped by a bushing 35 of electricalinsulating material, such bushing having a flange 36 seated against theshoulder portion 32 of member 29. A metal sleeve 37 is disposed aboutthe bushing 35. e

The plate 25 of capacitor and mount 21 is formed with a circular centralopening snugly embracing a portion of bushing 35. One face of plate 25is in intimate physical contact with the end of sleeve 37 opposite toflange 36, and the plate 25 is secured in place on the hub by a nut 38threaded on tip portion 34 of the hub and separated from plate 25 by acupped, annular washer of electrical insulating material 39. When not 38is threaded into place, the plate 25 is clamped rigidly between washer39 and the adjacent end of sleeve 37 and is electrically insulated fromhub 29 by bushing 35 and washer 39. In this way good electrical contactis obtained between the plate 25 and the sleeve 3'7. The plate 24 isformed with a central opening which is substantially larger than that ofplate 25. Hence, the plate 24 does not contact metal sleeve 3'7, as seenin FIG. 3. i

The centrifugal switch 22 includes a movable contact 40 carried by aresilient leaf spring 41, and a fixed contact 42 carried by a metalscrew 43, the screw extending chordwise with respect to the circularperiphery of plate 25. The screw 43 extends through a threaded openingin a flange 44 which is provided on the plate 25 and is perpendicularthereto. Contact 42 is thus mounted on and electrically connected toplate 25. The position of fixed contact 42 can be adjusted by turningscrew 43 on flange 44 after which a locknut 45 can be tightened.Resilient contact-carrying spring 41 is mounted on and electricallyconnected to plate 24 by bracket 46, as seen in FIGS. 2 and 4.

When the shaft 15 is rotating below a predetermined speed, switch 22 isbiased to its normally closed position by the action of resilient spring41, the spring force prevailing over the centrifugal force developed dueto rotation of the motor shaft. As the speed of the motor increases, thecentrifugal force tending to open switch 22 increases so that, attheproper time, the centrifugal force overcomes the spring force andcontacts 40 and 42 are separated.

The resistor assembly 23 comprises a ceramic resistor element 47 havingthe configuration of a short cylinder, one circular face thereof beingin contact with the outer face of plate 24 of capacitor and mount 21.The resistor 47 is held firmly in place and in good contact with plate24 by a metal bow spring 48 acting on a metallic hold down and coolingplate 49 which bears against the opposite circular face of the resistor47, the ends of the spring 48 being fixed to flanges 50 which areprovided on the plate 25 and extend axially of the motor shaft 15.

The spring 48 bows toward plate 49 and has sufiicient normal curvatureto cause the spring to be held under compression when the assembly iscompleted. Hence, considering the circular faces of resistor element 47as being the terminals thereof, one terminal is connected to the plate25 by the flanges 50, flat bow spring 48 and hold down and cooling plate49, while the other terminal is in direct contact with the plate 24.Accordingly, resist Patented July 13, 1965 9 tor 47 is connected betweenplates 24 and 25 to provide the circuit seen diagramamtically in FIG. 5.

One terminal of winding 13 is connected by conductor 53, FIG. 5, to acarbon brush 54 so mounted as to be maintained in contact with sleeve37, FIG. 3. It will be understood that sleeve 37 rotates with shaft 15,and that a conductive path is provided through brush 54, sleeve 37 andplate 25 to plate 24 either through switch 22 (when the switch isclosed) or through resistor 47.

n its face opposite dielectric sheet 26, plate 24 has a freely exposedannular arm concentric with the axis of the shaft 15. Bearing againstthis area is a second carbon brush 55, mounted in any suitable fashion,the brush 55 being connected via conductor 56 to one of the usualcommutator brushes for the motor. When switch 22 is in its normallyclosed position, and manual switch 17 is closed, a circuit is completedfor windings 13 and 1 via brush 54, sleeve 37, plate 25, switch 22,plate 24 and brush 55, resistor 47 being short-circuited. When the speedof shaft increases by an amount sufficient to cause centrifugal switch22 to open, the circuit is then completed for windings l3 and 14 viabrush 54, sleeve 37, plate 25, the flanges 5% provided on plate 25,resistor 47, the plate 24 and brush 55. Hence, the resistor 4-7 isconnected in series relation with the windings 13 and 14 and the motoris slowed down sufiiciently to cause centrifugal switch 22 to close sothat resistor 47 will again be shortcircuited.

Since movable contact 40 of switch 22 is connected to plate 24 and fixedcontact 42 is connected to plate 2 5, it will be understood that thecapacitor formed by the plates 24 and 25 and the dielectric sheet 2dtherebetween is connected electrically across the centrifugal switch andwill be effective in the usual manner to prevent the switch fromcreating radio and television interference.

In accordance with this invention, the resilient contact carrying spring41 is fixed to one face of bracket 46, which extends axially of themotor shaft 15 irom the plate 24 to which it is secured, and forms partof a cantilevered resilient arm A having a second resilient spring 57fixed to the opposite face of the bracket 46. The resilient spring 41 isapertured to receive a threaded set screw 53 which is adapted to bearagainst the resilient spring 57, as shown in FIG. 2. With thisarrangement the distance or separation of the resilient springs 41 and57 by the set screw 58 can be adjusted to vary the tension of theresilient arm A upon which the movable contact an is mounted and in thisway nicely controls the speed at which the contacts and 42 separateresponsive to centrifugal force developed by the motor against thebiasing action of the resilient arm A tending to keep the contacts 4nand 42 closed.

The arrangement provided for adjusting the tension of the resilient armsA possesses the advantage that the biasing action of the resilient armcan be varied without the need for rotating the contacts 40 and 42 withrespect to one another. Accordingly, after the opposing faces of thecontacts 40 and 42 have become worn during operation of the motor andgood electrical contact therebetween is obtained, it is not necessary togrind the opposing faces of the contacts before the biasing action ofthe resilient arm A, upon which the movable contact is carried, isvaried or changed.

In view of the foregoing, it will now be understood that my improvedswitch device includes an operating contact arm A having a contact 49thereon normally biased toward a first position, that is, toward theaxis about which the device moves in an arcuate path. Further, thecontact 40 on the swingable contact arm A is movable under centrifugalforce, an applied force, to a second position away from the axis. Theoperating contact arm A embodies two cantilevered resilient springs 41and 57 abreast of one another, each of the resilient springs 41 and 57being movable with respect to the other. screw 58 functions as anadjustable element for transmit- The ting force betwen the resilientsprings 41 and 57 to vary the biasing of the contact arm A to the firstposition.

The regulator illustrated is particularly useful in connection withsmall, high speed electrical motors of the type employed to drivecalculating machines, cash registers, and the like, where speedregulation is important because the motor is intermittently loaded.

While a particular embodiment of the invention has been shown anddescribed, such variations and modifications are contemplated as fallwithin the true spirit and scope of the invention, as pointed out in thefollowing claims.

What is claimed is:

l. A switch device including an operating contact arm having a contactthereon, said contact arm comprising at least two members normallybiased toward a first position and movable under an applied force to asecond position, each of said members being movable with respect to theother, and adjustable force transmitting means functioning between saidmembers to vary the biasing of said contact arm to said first position.

2. A centrifugal switch device including an operating contact arm havingcontact thereon adapted to be normally biased toward an axis about whichthe device moves in an arcuate path, a mounting for said contact arm topermit movement thereof away from said axis under centrifugal force,said contact arm comprising at least two resilient members each of whichis relatively movable with respect to the other, and force transmittingmeans functioning between said resilient members.

3. A centrifugal switch device including an operating cont act armhaving a contact thereon adapted to be normally biased toward an axisabout which the device moves in an arcuate path, a mounting for saidcontact arm to permit movement thereof away from said axis undercentrifugal force, said contact arm comprising at least two resilientmembers each of which is relatively movable with respect to the other,and adjustable force transmitting means functioning between saidresilient members to vary the biasing of said contact arm toward saidaxis.

4. A centrifugal switch device including a part adapted to be mounted ona shaft rotatable about an axis, an operating contact arm mounted onsaid part, said contact arm having a contact normally biased toward saidaxis and movable away from said axis under centrifugal force, saidcontact arm comprising a pair of cantilevered resilient members upon one.of which said contact is carried, each of said resilient members beingrelatively movable with respect to the other, and means functioningbetween said resilient members for transmitting force from the other ofsaid resilient members to said contact carrying resilient member.

5. A centrifugal switch device including a part adapted to be mounted ona shaft rotatable about an axis, an operating contact arm mounted onsaid par-t, said contact arm having a contact normally biased towardsaid axis and movable away from said axis under centrifugal force, saidcontact arm comprising a pair of cantilevered springs abreast of oneanother, said contact being carried by one of said springs, andadjustable force transmitting means functioning between said springs tovary the biasing of said contact arm toward said axis.

6. A centrifugal switch device including a part adapted to be mounted ona shaft rota-table about an axis, an operating cantilevered resilientcontact arm mounted on said par-t, said contact arm having a contactthereon normally biased toward said axis, said arm being swing-able awayfrom said axis under centrifugal force and comprising at least a pair ofresilient members abreast of one another, said contact being carried byone of said resilient members, and adjustable force transmit-ting meansfunctioning between said resilient members to vary the biasing of saidcontact arm toward said axis, said last-mentioned means comprising anelement which is carried by one of said resilient members and movabletoward and from said other resilient member.

7. A centrifugal switch device including a part adapted to be mounted ona shaft rotatable about an axis, an operating contact arm mounted onsaid part, said contact arm having a contact thereon normally biasedtoward said axis, said arm being swingable away from said axis undercentrifugal force and comprising at least a pair of cantileveredresilient springs abreast of one another, and force transmit-ting meansfunctioning between said springs.

8. A centrifugal switch device including a part adapted to be mounted ona shaft rotatable about an axis, an operating contact arm having acontact thereon normally biased toward said axis,said tar-m beingswingable away from said axis under centrifugal force and comprising apair of cantilevered resilient springs abreast of one another, andadjustable force transmit-ting means functioning between said resilientsprings, said last-mentioned means including an element which is carriedby one of said resilient springs and engages said other resilientspring, said element being adjustable on said one resilient springtoward and from said other resilient s aring.

References Cited by the Examiner UNETED STATES PATENTS 1,855,703 4/32Cloud 20)80 2,387,646 10/45 Crosman ZOO-89 2,715,164 8/55 Hufnagel 2003O2,760,027 8/56 Riley 200-466 2,997,559 8/61 Caton 20()80 2,999,139 9/61Lee 2O()-80 BERNARD A. GILHEANY, Primary Examiner.

MAX L. LEVY, Examiner.

1. A SWITCH DEVICE INCLUDING AN OPERATING CONTACT ARM HAVING A CONTACTTHEREON, SAID CONTACT ARM COMPRISING AT LEAST TWO MEMBERS NORMALLYBIASED TOWARD A FIRST POSITION AND MOVABLE UNDER AN APPLIED FORCE TO ASECOND POSITION, EACH OF SAID MEMBERS BEING MOVABLE WITH RE-